Record Details
Bright air : geoprocessing thermal imagery to map the nocturnal dynamics of the boundary layer in a mountain valley
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Bright air : geoprocessing thermal imagery to map the nocturnal dynamics of the boundary layer in a mountain valley |
| Names |
Johnson, Christopher (Raymond Christopher)
(creator) Thomas, Christoph (advisor) |
| Date Issued | 2015-03-12 (iso8601) |
| Note | Graduation date: 2015 |
| Abstract | A thermal infrared (TIR) camera is used to remotely sense the foliage temperature in a mountain valley. The foliage temperature is used as a proxy for air temperature and can be used to study and map the dynamics of the nocturnal, weak-wind boundary layer in this valley. All radiative flux not originating from the forest canopy must be filtered out of the captured imagery. Once the image has been filtered it must be georeferenced and orthorectified before useful analyses can be performed. After geoprocessing is complete, a spatially explicit time series of temperatures for an entire forested mountain valley will be available for further exploitation. The geoprocessed thermal imagery can, when combined with various data recorded in situ, yield data sets such as sensible heat flux at the canopy surface, potential temperature profiles, the adiabatic lapse rate in the watershed, the state of static stability in the watershed, and to map cold-air pool dynamics. Evidence was established that two concepts underlying the Bright Air study are valid for this study site. The first is that a TIR camera can accurately record foliage canopy temperature. The second is that on clear nights, foliage canopy temperature can be a proxy for the temperature of air immediately adjacent to the canopy. This study indicates that a TIR camera can accurately measure foliage canopy temperature on clear nights. Furthermore, the study indicates that on clear or intermittently cloudy nights, foliage canopy temperatures as measured by a TIR camera can be a proxy for the temperature of air immediately adjacent to the canopy. A process to georeference and orthorectify thermal imagery was selected and a tool to geoprocess the thermal imagery was created. Vertical profiles of potential temperature in the study area were created for times of interest and classified according to flow regimes. Dominant flow regimes were found to correlate well with earlier studies. Cold-air pool formation and drainage evolution were characterized for several clear nights. Nocturnal cold-air dynamics in the study area do not agree with common explanations of behavior of cold-air pools and drainage in mountain valleys. Up-valley flow patterns in the watershed indicate that nocturnal flows in mountain valleys are not driven solely by gravity. For the nights studied, flows in the watershed interact with flows from other connected basins and have identifiable patterns and typical evolutionary stages. |
| Genre | Thesis/Dissertation |
| Access Condition | http://creativecommons.org/licenses/by-nd/3.0/us/ |
| Topic | Cold Air Pooling |
| Identifier | http://hdl.handle.net/1957/55592 |
